Method and Apparatus for Improving Performance and Range of Conventional Power Tongs

ABSTRACT

A jaw assembly for gripping tubular goods in a power tong. The jaw assembly has at least three (3) jaw members: a first primary jaw member, a second primary jaw member, and at least one intermediate jaw member disposed between the first and second primary jaw members. The jaw assembly can be easily and conveniently installed within a conventional 2-jaw power tong without extensive modification thereto, and increases the pipe gripping capacity of the tong (and particularly small size pipe) without damaging the pipe.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention pertains a method and apparatus for improving performance of conventional power tongs. More particularly, the present invention pertains to a method and apparatus for increasing gripping strength of, as well as the application of torque by, power tongs. More particularly still, the present invention pertains to a method and apparatus for quickly and affordably modifying conventional power tongs to improve performance of said conventional power tongs.

2. Brief Description of the Related Art

The present invention generally relates to an apparatus, commonly referred to as a power tong, that is typically used to connect (“make up”) and disconnect (“break out”) threaded connections between lengths of tubular goods including, without limitation, sections of pipe (commonly referred to as “joints”). Said tubular goods can be used in connection with, among other applications, the drilling of oil, gas, water, and other mineral wells, as well as the installation of pipelines.

The size, weight and other specifications of a particular power tong can vary. Such specifications frequently depend upon the torque capacity and the size(s) of tubular goods that can be successfully gripped by said power tong without causing objectionable damage to said tubular goods. Such damage can include, without limitation, alteration of the cross-sectional circular geometry of a tube body (“crushing”), and/or disfigurement of the surface where said tube body is gripped by the power tong (“scarring”).

A conventional power tong typically comprises a plurality of gripping elements that are used to selectively grip portions of an outer surface of a pipe section, and to transfer torque between rotating elements of said power tong and said pipe that is being gripped by said power tong. The transfer of torque from a power tong to a pipe section is generally dependent upon the sum of forces acting tangentially upon the outside diameter (OD) of said pipe section. However, the smaller the OD of a pipe section, the greater the radial clamping forces must be in order to apply the required tangential forces for a given torque to be transferred from a power tong to a pipe section without slippage of the gripping elements of the tong on the tube body.

With all power tongs there is a limit to the ratio of tangential force versus radial clamping force applied to a pipe section (typically at the interface between gripping elements of a power tong and said pipe) to avoid slippage and objectionable scarring of the pipe surface. As a result, the radial clamping forces generated by a conventional 2-jaw power tong designed for a given maximum size pipe section typically will not be sufficient to transfer torque to a pipe section having a significantly smaller OD without causing damage to the pipe surface. (Although this limitation regarding smaller pipe OD will vary depending upon the specific equipment and tong gripping elements used, it is typically in the range of 45 to 55% of the maximum pipe size for which a particular power tong is intended). Conversely, designing a power tong to apply sufficient clamping forces to a much smaller pipe OD can result in application of excessive clamping forces (and resultant crushing or other damage to a pipe) when said power tong is used on a pipe section having a larger OD.

Generally, damage to pipe that is gripped by a power tong can be minimized by increasing the contact area between gripping element(s) of said power tong and the outer surface of said pipe. However, excessive contact area may result in insufficient penetration of the gripping elements into the outer surface of a pipe, particularly when coatings, contaminants, scale and/or other materials are present on the surface. Thus, increasing the contact area in this manner can sometimes result in insufficient penetration of gripping element(s) into said pipe surface, thereby resulting in “skidding” or slippage around the pipe, often resulting in significant damage to the pipe surface. As such, an optimal power tong design typically requires balancing many factors including, without limitation, pipe OD and surface hardness, torque required to make up and/or break out threaded connections, and the available clamping forces provided by the power tong.

A common arrangement for conventional power tongs comprises two opposing jaw members positioned within a rotating assembly of said power tong. Said jaw members are typically energized (and moved radially inward) by cam surfaces formed along the inner surface of a ring gear of the power tong. Said two jaw members may articulate from hinge pins near the rear of a cage plate opening, or they may slide radially inward within guides. It has been observed that such a conventional two-jaw arrangement frequently provides a balance between the maximum pipe OD size that can be gripped, the overall size of the power tong and the torque that said power tong can apply, as well as other constraints such as passage of a pipe section into and out of the throat of the power tong.

Clamping force generated by a power tong at a given torque can then be optimized for the two jaw members and the range of pipe OD sizes that said power tong can effectively grip. However, applying the same torque to a pipe with a smaller OD size will often result in slippage and damage to a pipe surface, unless even greater clamping force can be generated.

Thus, there is a need for an improved and affordable jaw apparatus that can be quickly and efficiently installed in conventional power tongs to replace existing jaw assemblies of said power tongs, while improving performance and/or range of said power tongs. The improved jaw apparatus should permit a given power tong to effectively grip and apply torque to a broader range of pipe OD sizes without causing damage to the gripped pipe including, without limitation, crushing or scarring.

SUMMARY OF THE PRESENT INVENTION

In a preferred embodiment, the present invention comprises a jaw assembly having an arrangement of least three (3) cooperating jaw members with gripping elements connected or integral to each of said jaw members. The jaw assembly of the present invention can replace dual jaw members of a conventional 2-jaw power tong. Notwithstanding the foregoing, it is to be understood that the jaw assembly of the present invention can also replace jaw members of other conventional power tongs having more than two jaws. The gripping assembly of the present invention beneficially permits effective gripping of pipe sections at or below designed pipe diameter/OD design limits for a particular power tong, while reducing undesirable damage to said pipe sections gripped by said power tong.

The jaw assembly of the present invention can be quickly and efficiently installed within a power tong in similar manner as conventional jaw members, with little or no modification to said power tong. The jaw members of the jaw assembly of present invention can be interconnected directly, or through at least one intermediate component(s), in order to function cooperatively to apply radial clamping forces to a pipe section, and to transfer torque from a power tong to said pipe.

In a preferred embodiment, at least two primary jaw members of the jaw assembly of the present invention are energized (and move radially) by cam surface(s) of a ring gear of a conventional power tong. At least one intermediate jaw member(s) is pivotally attached to said primary jaw members, while remaining substantially stationary with the rotating assembly. Radial clamping forces generated by said primary jaw members (directly activated by said cam surface(s)) are reacted by the intermediate jaw member(s) of the assembly, thereby increasing the total number of gripping elements that can engage against the external surface of a pipe section gripped thereby.

The jaw assembly of the present invention improves the gripping force applied by a conventional power tong by imparting additional normal force(s) to the external surface of a pipe section including, without limitation, via said (additional) intermediate jaw member(s). Because said intermediate jaw member(s) merely react to the force generated by cams acting on the primary jaw member(s) of the assembly, said intermediate jaw member(s) provide additional gripping force at the external surface of a pipe section (including a pipe section having a smaller OD). As a result, said gripping force acts to prevent slippage of said jaw member(s) on a pipe section at a given torque applied by a ring gear of a power tong, all without changing cam geometry of said power tong.

An additional advantage of the present invention is the ability to better distribute forces (both radial and tangential) applied to a pipe section around the outer circumference of said pipe section, thereby reducing the risk of permanently distorting the circular geometry of said pipe and/or excessively damaging the external surface of the pipe by gripping elements. By applying forces by at least three gripping elements arranged around the circumference of a pipe body—instead of only two gripping elements that are diametrically opposed to each other—the arc of unsupported area between said gripping elements is reduced, resulting in a lower risk of pipe wall extrusion in areas between the gripping elements of the jaw members.

A power tong with a pipe size range limitation can be augmented by removing a conventional (two) jaw assembly and installing the jaw assembly of the present invention described herein. The additional jaw member(s) (and associated gripping element(s)) of the present invention provide increased tangential force capacity, while better distributing the required clamping force around the outer circumference of a pipe section, thereby extending the useful working range of said conventional power tong. As a result, required inventory of power tongs can be reduced while still meeting demands for a larger range of pipe sizes that can be serviced by said power tongs.

It is to be observed that other embodiments of the jaw assembly of the present invention can also function in much the same manner in a power tong which generates clamping forces hydraulically, mechanically, or by other means.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description of the preferred embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, the drawings show certain preferred embodiments. It is understood, however, that the invention is not limited to the specific methods and devices disclosed. Further, dimensions, materials and part names are provided for illustration purposes only and not limitation.

FIG. 1 depicts a side perspective view of a conventional power tong.

FIG. 2 depicts an overhead view of a first embodiment of jaw members of a conventional power tong gripping a first pipe section.

FIG. 3 depicts an overhead view of a second embodiment of jaw members of a conventional power tong gripping a second, smaller pipe section.

FIG. 4 depicts an overhead view of jaw members of a conventional power tong gripping a pipe section and causing damage to said pipe section.

FIG. 5 depicts an overhead view of a portion of a conventional power tong including a ring gear and jaw members.

FIG. 6 depicts an overhead view of the jaw assembly of the present invention installed within the ring gear of a conventional power tong.

FIG. 7 depicts an overhead view of the jaw assembly of the present invention gripping a pipe section.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Referring to the drawings, FIG. 1 depicts a side perspective view of a conventional power tong 100. Said conventional power tong 100 generally comprises a frame member 101 supporting a cage (or cage plates) 102. A moveable door member 103 can selectively move between a first closed position (depicted in FIG. 1 ) blocking access to throat 104 that leads into a central space defined within said cage (or cage plates) 102, and a second open position wherein said throat 104 is substantially unobstructed. Motor 106 (which is typically hydraulically powered) supplies torque (typically via additional gears, belts, or other drive components) to a ring gear 105, causing said ring gear to selectively rotate within cage (or cage plates) 102.

Still referring to FIG. 1 , a common arrangement utilizes two (2) jaw members 130 disposed approximately 180 degrees, more or less, from each other around said ring gear. Each of said jaw members 130 can be equipped with gripping elements 140. Conventional power tongs (such as power tong 100 depicted in FIG. 1 ) are typically equipped with two (2) jaw members 130 disposed in diametrically opposing relationship. When energized, said jaw members 130 pivot or move radially inward and said gripping elements 140 engage against the outer surface of a pipe section in order to grip said pipe section.

FIG. 2 depicts an overhead view of a first embodiment of opposing jaw members 130 of a conventional power tong gripping a first pipe section 200. Each of said jaw members 130 has a gripping element 140 (also commonly referred to as a “die”); Further, each of said gripping elements 140 can comprise a plurality of radially inwardly facing teeth or protrusions. When said gripping elements 140 of said jaw members 130 are engaged against pipe section 200, said teeth of said gripping elements 140 can contact said outer surface of pipe section 200. Said teeth of said gripping elements 140 act to increase frictional forces existing between said jaw members 130 and said outer surface of pipe section 200, thereby helping said jaw members 130 grip against the outer surface of said pipe section 200.

Said jaw members 130 and gripping elements 140 are used within a conventional power tong to selectively grip a portion of an outer surface of a pipe section, and to transfer torque from rotating elements of said power tong to a pipe section. As previously noted, the transfer of torque from a power tong to a pipe section is generally dependent upon the sum of forces acting tangentially upon the outer surface of said pipe section. The smaller the OD of a pipe section, the greater said tangential force must be for a given torque to be transferred from a power tong to a pipe section without slippage of the gripping elements 140 along the outer surface of the pipe body.

FIG. 3 depicts an overhead view of a second embodiment of jaw members 130 of a conventional power tong gripping a second pipe section 300. Each of said jaw members 130 has a gripping element 240, while each of said gripping elements 240 has a plurality of radially inward facing teeth or protrusions. Said teeth of said gripping elements 240 can be selectively engaged against the outer surface of pipe section 300. It is to be observed that pipe section 300 depicted in FIG. 3 has a significantly smaller outer diameter than pipe section 200 depicted in FIG. 2 . As a result, the contact area of gripping members 240 against pipe section 300 is less than the contact area of gripping members 140 on pipe section 200.

FIG. 4 depicts an overhead view of jaw members 130 of a conventional power tong gripping a pipe section 200. Each of said jaw members 130 has a gripping element 140, while each of said gripping elements 140 has a plurality of radially inwardly facing teeth or protrusions used to contact and grip against the external surface of pipe section 200. As depicted in FIG. 4 , a conventional 2-jaw arrangement—wherein gripping members 140 are more or less diametrically opposed to each other—results in significant areas 210 of pipe section 200 that are unsupported or otherwise contacted by any gripping member. Application of excessive clamping forces by said opposing jaw members 130 can result in extrusion of said pipe section 200 between said jaw members, particularly in unsupported areas 210, thereby negatively altering the circular tube shape of pipe section 200.

FIG. 5 depicts an overhead view of a portion of a conventional power tong including a ring gear 105 and jaw members 130, such as shown in conventional power tong 100 depicted in FIG. 1 . A common arrangement, as depicted in FIG. 5 , utilizes two jaw members 130 disposed within a cage (or cage plates) of power tong that are more or less diametrically opposed to each other; said jaw members 130 are positioned around the inside circumference of said ring gear 105. Said jaw members 130 are energized by cam surfaces 107 machined into the inner surface of ring gear 105. The two jaw members 130 may articulate from hinge pins 120, or may slide within guides, in order to move radially inward and into engagement with a pipe section to be gripped by a power tong.

A two-jaw arrangement as depicted in FIGS. 2 through 5 is often employed in conventional power tongs to balance variables such as maximum pipe OD size that can be gripped, overall size of a power tong, torque that a power tong can apply to pipe, and other constraints such as passage of pipe into and out of the throat of a power tong. In this configuration, the clamping force generated by opposing jaw members at a given torque, and the range of allowable pipe sizes that said power tong can successfully grip for that torque, can be determined. However, applying the same torque to a pipe section with a smaller OD outside of said range will frequently result in slippage and damage to the surface of the pipe, unless even greater clamping force can be generated.

FIG. 6 depicts an overhead view of jaw assembly 10 of the present invention installed within a ring gear 105 of a conventional power tong. In a preferred embodiment, jaw assembly 10 comprises an arrangement of at least three (3) jaw members; said at least three (3) jaw members generally comprise at least two (2) primary jaw members 50 and at least one intermediate jaw member 60 disposed between said primary jaw members 50. Gripping elements 40 are connected to or integral to each of said jaw members 50 and 60.

Jaw assembly 10 can replace a conventional 2-jaw apparatus of a power tong, particularly when gripping pipe sizes near or below the normal pipe size limits of said power tong. Jaw assembly 10 can be installed in a similar manner as conventional jaws, with little or no modification to a conventional power tong. The jaw members of the invention cooperate to apply radial clamping forces to a pipe section. Primary jaw members 50 are activated by cam surface(s) 10 of ring gear 105, while pivotally attached to the intermediate jaw member(s) 60. The radial clamping forces generated by primary jaw members 50 (that are directly energized by cam surface(s) 10) are reacted by intermediate jaw member(s) 60, thereby increasing the total number of gripping elements 40 that contact and engage against the outer surface of a pipe section.

It is to be observed that the present invention is described herein primarily in connection with replacement of conventional 2-jaw apparatus of a conventional power tong. However, notwithstanding anything to the contrary contained herein, it is to be understood that jaw assembly 10 of the present invention can also replace jaw members of other conventional power tongs having more than two jaws—that is, conventional power tongs having three or more jaws members.

FIG. 7 depicts an overhead view of jaw assembly 10 of the present invention gripping a pipe section 200. An advantage of jaw assembly 10 of the present invention is the ability to better distribute forces (both radial and tangential) that are applied to pipe section 200 around the circumference of said pipe section, thereby reducing the risk of permanently distorting the circular geometry of pipe section 200 and/or unacceptable damage to the external surface of said pipe section 200 by gripping elements 40. By applying the clamping forces through at least three gripping elements 40 arranged around the outer circumference of pipe section 200, instead of only two that are diametrically opposed as with a conventional 2-jaw apparatus, the arc of unsupported area 210 existing between gripping elements 40 is greatly reduced, thereby significantly lowering the risk of extruding the pipe wall between the gripping elements 40 of the jaw members 50 and 60.

Jaw assembly 10 of the present invention improves the capacity of a conventional power tong by applying additional normal force(s) to the external surface of gripped pipe with (additional) intermediate jaw member(s) 60. Because said intermediate jaw member(s) 60 merely react to the force generated by cams acting on primary jaw member(s) 50, it can thereby provide the additional tangential force required at the outer surface of a smaller pipe in order to prevent slippage for a given torque, without changing the cam geometry.

A power tong having a conventional 2-jaw assembly can be quickly and efficiently reconfigured with jaw assembly 10 of the present invention. The additional jaw(s) and gripping element(s) of said jaw assembly 10 provides more tangential force capacity, while better distributing the required clamping force around the circumference of the pipe, thereby extending the useful range of the power tong.

The above-described invention has a number of particular features that should preferably be employed in combination, although each is useful separately without departure from the scope of the invention. While the preferred embodiment of the present invention is shown and described herein, it will be understood that the invention may be embodied otherwise than herein specifically illustrated or described, and that certain changes in form and arrangement of parts and the specific manner of practicing the invention may be made within the underlying idea or principles of the invention. 

What is claimed:
 1. A gripping apparatus for gripping the external surface of a pipe with a power tong comprising: a) a first jaw member disposed at a first end of said gripping apparatus; b) a second jaw member disposed at a second end of said gripping apparatus; and c) at least one intermediate jaw member disposed between said first jaw member and said second jaw member, wherein said at least one intermediate jaw member is pivotally attached to said first jaw member and said second jaw member.
 2. The gripping apparatus of claim 1, wherein said gripping apparatus is configured to be installed in a power tong without requiring modification of said power tong.
 3. The gripping apparatus of claim 1, wherein said first jaw member and said second jaw member are engaged against said external surface of said pipe by cam surfaces of a ring gear.
 4. The gripping apparatus of claim 3, wherein said at least one intermediate jaw member is not engaged against said external surface of said pipe by a cam surface of said ring gear.
 5. The gripping apparatus of claim 4, wherein engagement of said first jaw member and said second jaw member against said outer surface of said pipe causes said at least one intermediate jaw member to contact said outer surface of said pipe.
 6. The gripping apparatus of claim 1, wherein said first jaw member, said second jaw member and said at least one intermediate jaw member are equipped with gripping dies.
 7. The gripping apparatus of claim 1, wherein said jaw members cooperate to apply radial clamping force from said power tong to said pipe.
 8. The gripping apparatus of claim 7, wherein said radial clamping force is distributed more evenly around the circumference of said pipe compared to a gripping apparatus having only two jaws.
 9. The gripping apparatus of claim 1, wherein said jaw members cooperate to apply tangential force from said power tong to said pipe.
 10. The gripping apparatus of claim 9, wherein said tangential clamping force is distributed more evenly around the circumference of said pipe compared to a gripping apparatus having only two jaws.
 11. A method for gripping a pipe with a power tong comprising: a) installing a gripping apparatus in said power tong, wherein said gripping apparatus comprises: i) a first jaw member disposed at a first end of said gripping apparatus; ii) a second jaw member disposed at a second end of said gripping apparatus; and iii) at least one intermediate jaw member disposed between said first jaw member and said second jaw member, wherein said at least one intermediate jaw member is pivotally attached to said first jaw member and said second jaw member; b) engaging said first jaw member and said second jaw member against said external surface of said pipe with cam surfaces of a ring gear; and c) engaging said at least one intermediate jaw member against said external surface of said pipe, wherein said at least one intermediate jaw member is not contacted by a cam surface of said ring gear.
 12. The method of claim 11, wherein said gripping apparatus is configured to be installed in a power tong without requiring modification of said power tong.
 13. The method of claim 11, wherein said first jaw member, said second jaw member and said at least one intermediate jaw member are equipped with gripping dies.
 14. The method of claim 11, wherein said jaw members cooperate to apply radial clamping force from said power tong to said pipe.
 15. The method of claim 14, wherein said radial clamping force is distributed more evenly around the circumference of said pipe compared to a gripping apparatus having only two jaws.
 16. The method of claim 11, wherein said jaw members cooperate to apply tangential force from said power tong to said pipe.
 17. The method of claim 16, wherein said tangential clamping force is distributed more evenly around the circumference of said pipe compared to a gripping apparatus having only two jaws. 